West and Central African Rift System

{{Short description|Rift system in Africa composed of two Cretaceous-era sub-systems}}

File:Central African Shear Zone.svg labeled CASZ]]

The West and Central African Rift System (WCARS) is a rift system composed of two coeval Cretaceous rift sub-systems, the West African Rift sub-system (WAS) and the Central African Rift sub-system (CAS).{{Cite journal |last=Bosworth |first=William |date=20 October 1992 |title=Mesozoic and early Tertiary rift tectonics in East Africa |url=https://linkinghub.elsevier.com/retrieve/pii/004019519290014W |journal=Tectonophysics |language=en |volume=209 |issue=1–4 |pages=115–137 |doi=10.1016/0040-1951(92)90014-W|bibcode=1992Tectp.209..115B |url-access=subscription }} These are genetically related, but are physically separated and show structural differences.{{cite web|last1=Loule|first1=Jean-Pierre|last2=Lumbomil|first2=Pospisil|title=The Logone Birni Basin (LLB) in Northern Cameroon: Transition Between the West African Rift Sub-System (WAS) and the Central African Rift Sub-System (CAS); Tectonic and Geophysical Models|url=http://www.searchanddiscovery.com/pdfz/documents/2009/50171loule/ndx_loule.pdf.html|website=AAPG Search and Discovery|publisher=AAPG|accessdate=31 January 2016}} The Logone Birni Basin constitutes a transitional area between the two sub-systems.

The WCARS is older than the East African Rift System.

Formation

The West and Central Africa Rift System formed from the Early Cretaceous separation of Africa and South America.{{Citation |last1=Olsen |first1=K.H. |title=Chapter 13: West and Central African Rift System |date=2006 |url=http://dx.doi.org/10.1016/s0419-0254(06)80005-4 |work=Continental rifts:evolution, structure, tectonics |pages=3–26 |access-date=2023-10-24 |publisher=Elsevier |isbn=978-0-444-89566-0 |last2=Morgan |first2=P.|doi=10.1016/s0419-0254(06)80005-4 |url-access=subscription }} This rifting almost tore apart the African continent but instead formed a complex system of extensional, wrench and pull-apart basins.{{Cite journal |last1=Fairhead |first1=J. D. |last2=Green |first2=C. M. |last3=Masterton |first3=S. M. |last4=Guiraud |first4=R. |date=2013-05-24 |title=The role that plate tectonics, inferred stress changes and stratigraphic unconformities have on the evolution of the West and Central African Rift System and the Atlantic continental margins |url=https://www.sciencedirect.com/science/article/pii/S0040195113001959 |journal=Tectonophysics |volume=594 |pages=118–127 |doi=10.1016/j.tecto.2013.03.021 |bibcode=2013Tectp.594..118F |issn=0040-1951|url-access=subscription }} Such basins can be found from Nigeria and Cameroon on the Atlantic, east into Chad and the Central African Republic, through Sudan to Kenya on the Indian Ocean and north of Lake Chad extending into southern Algeria.

There were five major tectonic phases that formed the WCARS:{{Cite journal |last=Genik |first=G. J. |date=1992-10-30 |title=Regional framework, structural and petroleum aspects of rift basins in Niger, Chad and the Central African Republic (C.A.R.) |url=https://dx.doi.org/10.1016/0040-1951%2892%2990257-7 |journal=Tectonophysics |series=Geodynamics of Rifting, Volume II Case History Studies on Rifts: North and South America and Africa |volume=213 |issue=1 |pages=169–185 |doi=10.1016/0040-1951(92)90257-7 |bibcode=1992Tectp.213..169G |issn=0040-1951|url-access=subscription }}

The Pan African Crustal consolidation 750-550 Ma
Paleozoic-Jurassic platform development 550-130 Ma
Early Cretaceous rift 130-98 Ma; Late Cretaceous rift 98-75 Ma
Maastrichtian-Paleogene rift and emergence 75-30 Ma
Neogene-Recent emergence 30-0 Ma

References

Category:Mesozoic rifts and grabens

Category:Structural geology

Category:Plate tectonics

Category:Cretaceous geology